1. Field of the Invention
The present invention relates to a “multipoint” fuel injector device for an annular combustion chamber of a turbine engine such as an airplane turboprop or turbojet.
2. Description of the Related Art
In known manner, a turbine engine has an annular combustion chamber arranged at the outlet from a high-pressure compressor and provided with a plurality of fuel injector devices that are regularly distributed circumferentially at the inlet of the combustion chamber. A multipoint injector device comprises both a first venturi, within which a pilot injector is mounted centrally on the axis of the first venturi, which injector is fed continuously with fuel by a pilot circuit, and also a second venturi that is arranged coaxially around the first venturi. This second venturi has an annular chamber at its upstream end within which an annular ring is mounted, the ring being fed with fuel by a multipoint circuit. The ring has fuel injection orifices formed in a front face and aligned with orifices in a front face of the annular chamber so as to eject the fuel downstream and towards the outside of the second venturi.
The pilot circuit delivers a continuous flow of fuel at a rate that is optimized for low speeds, and the multipoint circuit delivers fuel at an intermittent rate that is optimized for high speeds.
Nevertheless, under the effect of the high temperatures due to the radiation from the flame in the combustion chamber, using an intermittent multipoint circuit presents the major drawback of giving rise to any fuel that stagnates inside the multipoint circuit clogging or coking when the multipoint circuit is switched off. These phenomena can give rise to coke being formed in the ring and in the fuel injection orifices of the multipoint circuit, thereby adversely affecting the spraying of fuel from the multipoint circuit, and thus affecting the operation of the combustion chamber.
In order to reduce this risk of coking, it is known from document EP 2 026 002 in the name of the Applicant to make use of the fuel pilot circuit to cool the multipoint circuit so as to reduce the formation of coke therein, by using two annular channels for passing fuel that are formed in the annular chamber radially inside and outside the annular ring, these two channels having their outlets connected to the pilot injector.
Nevertheless, such a configuration does not achieve a satisfactory reduction in the risk of coking for the fuel over the front face of the annular chamber, since said fuel remains strongly exposed to the thermal radiation generated by the combustion of fuel downstream therefrom.